What projector resolution do I need for presentations?

[badlydrawnboy]

I'm trying to figure out what type of projector to get for presentations. I do them about once a month, and in my local area. Portability isn't a huge factor.

I have a MacBook 13" with 1280 x 800 resolution. However, I always present with Keynote built in 1024 x 780. I like the 4:3 aspect ratio better for design purposes.

Here's my question: if I'm only ever using the 1024 x 780 presentations, is there any reason to get a 1280 x 800 projector? Or would I be fine with an XGA model?

 

[badlydrawnboy]

It's not that I want to change. I don't currently own a projector myself. I was using one at my school, but I have now graduated and need to buy my own. I'm trying to decide whether to buy a projector with a 16:9 or 16:10 native resolution, or an XGA model.